Bearings are one of the most important mechanical components in various mechanical structures. A bearing enables a rotational shaft mounted to the bearing to rotate freely with respect to a structure fixed with the bearing.
A typical bearing may include a plurality of rolling elements between the rotational shaft and an outer race. During operation, the rolling elements may rotate and/or move within the cavity between the rotational shaft and the outer race. In response to the rotational movement of the rolling elements, the rotational shaft may rotate freely with respect to the rotational axis of the bearing. Bearings may be made to permit the rotational axis to rotate at single rotational direction or both rotational directions according to different internal structures.